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101.
Juan M. Gracia Inmaculadade Hoyos Franscisco E. Velasco 《Linear and Multilinear Algebra》1999,46(1):25-49
We give safety neighbourhoods for the necessary conditions in the change of the Jordan canonical form of a matrix under small perturbations. We also obtain the minimum distance from an n × n complex matrix which has less than k nonconstant invariant factors (2≤ k≤ n) to the set of matrices which have more or equal to k. When k= 2, we get in particular the distance from a nonderogatory matrix to the set of derogatory matrices. 相似文献
102.
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104.
Javier Ramos Víctor L. Cruz Javier Martínez‐Salazar Mikael Brasse Pilar Palma Juan Campora 《Journal of polymer science. Part A, Polymer chemistry》2010,48(5):1160-1165
The present computational study was designed to study the polymerization of ethylene catalyzed by a new Ni‐based PymNox organometallic compound. Recently, we have synthesized and tested the behavior of this type of catalyst in olefin polymerization. It has been experimentally observed that the unsubstituted catalyst Ni2 (aldimino PymNox catalyst ) is less active than the methyl substituted Ni1 (acetaldimino PymNox catalyst ) analogue. The reactivity of both catalysts was examined using density functional theory (DFT) models. Our results indicate that the methyl substituted Ni1 introduces some additional steric hindrance that probably renders a more suitable catalyst conformation for the monomer incorporation. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1160–1165, 2010 相似文献
105.
Pilar Campíns Falcó Francisco Bosch Reig Ana Molina Benet 《Fresenius' Journal of Analytical Chemistry》1990,338(1):16-21
Summary This paper discusses the requirements and scope of application of the H-Point Standard Additions Method (HPSAM) for resolving binary mixtures. Various mixtures of dyes with extensively or completely overlapping spectra were assayed with accurate, precise results. The method thus developed was also applied to the spectrophotometric resolution of binary mixtures of phenol and o-cresol, the absorption bands of which lie in similar positions and feature similar absorptivities. 相似文献
106.
107.
A p-version finite element method has been used to calculate second-order pair and total correlation energies for closed-shell Mg and Ar. Comparison with the best results found in the literature suggests that the present values are the most accurate and that the method should perform comparatively better for heavier elements. © 1993 John Wiley & Sons, Inc. 相似文献
108.
The reaction between methyl N-acetyl-,β-didehydroalaninate and cyclopentadiene in the presence of several chiral Lewis acids is studied and the results obtained are compared with those described for the reactions of the same diene with chiral N-acetyl-,β-didehydroalaninates. In the presence of the titanium complex 24d methyl (1R,2R,4R) 2-acetamido-5-norbornen-2-carboxylate is preferably obtained. Thus, the reaction between methyl N-acetyl-(,β-didehydroalaninate and cyclopentadiene is a good method for the synthesis of (1S, 2R, 4R) 2-aminonorbomane-2-carboxylic acid. 相似文献
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Pilar G. Rodríguez Ortega Prof. Manuel Montejo Prof. Fernando Márquez Prof. Juan J. López González 《Chemphyschem》2015,16(7):1416-1427
The implementation of a strategy comprising the use of vibrational circular dichroism spectroscopy and DFT calculations allows determination of the solution‐state conformational distribution in (?)‐S‐cotinine, giving further proof of the extra conformer‐discriminating potential of this experimental technique, which may offer unique molecular fingerprints of subtly dissimilar molecular conformers of chiral samples. Natural bond orbital electronic structure calculations of the rotational barrier height between the two main conformers of the species indicate that hyperconjugative effects are the key force governing the conformational equilibrium. The negligible effect of the solvent’s polarity over both structure and conformational energy profile supports this result. 相似文献